Naftidrofuryl (also known as nafronyl), the acid oralate of which is marketed under the trade mark "Praxilene" is known for its action in connection with the treatments of arterial diseases of the limbs, circulatory disorders in the hands and feet, cerebral vascular disorders and the diffuse circulatory insufficiency in connection with elderly people.
In the form of a free base and a salt capable of being used therapeutically, it forms the subject of the U.S. Pat. No. 3,334,096 and French Special Medicament Pat. 3,843 M in the name of the present assignee.
Naftidrofuryl is the compound 3-(1-naphthyl)-2-tetrahydrofurfurylpropionic acid 2-(diethylamino)-ethyl ester and the acid oxalate of this compound (Praxilene) is represented by the formula ##STR1##
Praxilene is normally available for oral administration in the form of hard gelatine capsules and ampoules. However, such perorally administrable dosage forms give immediate release of the therapeutically active compound.
It is, however very important to prolong the therapeutic activity, thereby assuring an equal and continuous covering, especially of the cerebral circulation, for a complete period of 24 hours. Accordingly, research has been made to find a pharmaceutical preparation of naftidrofuryl, which obviates the disadvantages of a massive arrival of the active principle, followed by a decrease in the therapeutic effect due to the disappearance of the active principle in the circulating fundus. It is necessary to avoid every discontinuity in the cerebral irrigation, particularly during the second part of the night, when the circulation has to be intense. A discontinuity in the effect of the active product would produce the danger of causing a slowing down in the cerebral irrigation and could cause an ischemic cerebral disorder, between the completion of the effect from the first dosage of the medicine and the following dosage.